Question GPU OC with 240Hz monitor gives black screens

[Alfrys]

So I recently bought 1080p 240Hz monitor, upgrading from 75Hz. But actually running at 240Hz I can't use any GPU core OC even additional 1MHz on my AMD R9 390, because monitor keeps black screening few times a minute, no matter in game or browsing desktop (turns off panel with backlight then second later backlight comes back and screen gets back up, similar effect like changing some panel settings or refresh rate or signal loss). Running screen an 144Hz or lower doesn't provide any problems. I'm using DISPLAYPORT, HDMI on my graphics card can't run above 120Hz. Overclocking GPU via Afterburner, but different software gives same results like Radeon WattMan. Freesync on or off makes no difference. Using Win10 1903 build, went though 3 to 5 latest versions but currently using 19.11.3 GPU drivers.

Any help would be appreciated, can provide more info if needed.
Is there any way I can run 240Hz with GPU OC flawlessly?

System specs:
Monitor: Acer Nitro XF252QX
GPU: POWERCOLOR R9 390 (usual 24/7 stable oc: 1130MHz core, 1650MHz vram)
CPU: AMD RYZEN R5 3600 (stock clocks, with ram at 3600MHz)
MB: MSI TOMAHAWK B450

 

[rgd1101]

and make and model of the psu?

 

[Alfrys]

and make and model of the psu?

Cooler Master ATX G750M 80 PLUS Bronze almost 4 years old